Orca vs. Great White

If the whale and the shark are the same size and have the same maximum velocity then who eats whom, or who catches whom, is a matter of endurance rather than brute force of muscle activity. Therefore, a good way to explain it is to consider the physiological systems of the two species: sharks are heterothermic regulators (they have counter-current exchange vessels to trap heat from active muscles in their core), whales are endotherms with high body temperatures; sharks are fish and have gills to derive oxygen from seawater, whales are mammals that breathe air; they are both quite well streamlined for rapid velocity in water. The whale should be able to catch the shark every time because:

a) endothermic whales have much higher body temp than heterothermic sharks. The Q-10 effect would allow greater rates of protein activity (like muscle proteins), metabolism, and energy production in the whale’s muscles than in the shark’s. Higher temp plus more ATP to burn means faster and stronger acting muscles.

b) the lungs of the air-breathing whale can do gas exchange at much higher rates than the gills of the shark. There is much less oxygen in water, water is viscous and relatively slow to move across gill filaments; air has 21% oxygen, has practically zero viscosity, and moves in and out of respiratory systems very, very quickly, guaranteeing rapid and extensive O2  --  CO2  exhange.

Bottom line: the killer whale catches the shark eventually.